Evaluation of phenotypic tests to detect carbapenem-resistant Enterobacteriaceae in colonized patients hospitalized in intensive care units

Abstract

In this study, we aimed to evaluate the performance of different phenotypic tests to detect carbapenem-resistant Enterobacteriaceae.Three different phenotypic methods were evaluated: (1) combined-disk test of meropenem plus phenylboronic acid or EDTA reading after 24 h and 48 h; (2) selective/chromogenic read after 24 h and after 48 h; and (3) overnight selective enrichment broth containing 10 μg ertapenem disk followed by culture on MacConkey agar. A positive result in at least one of the methods was submitted to PCR for blaNDM-1, blaOXA-48, blaKPC, blaSPM-1, blaIMP, and blaGES detection.Carbapenem-resistant Enterobacteriaceae was detected in 31 (30.4%) of 102 rectal swabs evaluated. All isolates showed to be KPC-2-producing organisms. Results showed excellent agreement among the evaluated tests (positive and negative) (kappa = 0.88).It is important to state that combined-disk test with phenylboronic acid is not suitable for bacterial identification/isolation. Conversely, selective/chromogenic agar after 48h of incubation showed to be a useful tool, with the advantage of presumptive bacterial identification. Keywords: Carbapenems, Enterobacteriaceae, KPC, Surveillance